The invention relates generally to coal and biomass gasification systems and, more particularly, to a system for transporting solid particulate fuel to a gasifier that is most likely operated at high pressure.
In current commercialized gasification systems, solid particulate fuel such as coal is fed into gasifier using either slurry feed or dry feed technologies. Due to the limitation in making slurry using high-moisture content solid particulate fuel, a dry feed system is normally utilized to feed such solid particulate fuel into gasifiers. In existing dry feed systems, low rank coals may be dried to remove two-thirds, or more, of the inherent moisture present in the coal. This improves the flow characteristics of the dried solids in the dry feed system equipment and the overall efficiency of the gasifier. However, the overall power production of the plant is reduced since the drying process consumes a large amount of energy.
In chemical, petrochemical, and power industries, most of the reactors such as gasifiers or combustors are operated under high-pressure conditions. Feeding solid fuels or reactants into a high-pressure gasifier with a pressure range of about 100 to about 1000 psi is a significant challenge. In existing gasification systems, either a slurry feeding system or a lock-hopper dry feeding system is used to feed solid fuels into a high-pressure gasifier. But, not all kinds of solid particulate fuels can be converted to slurry with a fairly high solid concentration. Therefore, a slurry feeding system may not be suitable for all kinds of solid particulate fuels.
In lock-hopper dry feeding system, solid fuels must be dried to a certain level to avoid rat-holing or bridging in the lock-hopper and reach a reasonable reliability. For example, brown coal must be dried to a moisture-content of less than about 10 percent and bituminous coal must be dried to a moisture-content of less than about 2 percent. However, existing dry feeding technologies may not handle solid fuels without pre-drying to a certain level.
It would therefore be desirable to provide a dry feeding system that can feed solid particulate fuels with high moisture content into a high-pressure gasifier without a pre-drying process.